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Voltage drop calculator
Estimate DC voltage drop from current, one-way length and conductor resistance.
On this page
Round-trip voltage drop2V
Voltage drop0.87%
Load voltage228V
Calculator controls
How to calculate
Estimate DC voltage drop from current, one-way length and conductor resistance.
Round-trip voltage drop = 2*current*length*resistance; Voltage drop = 2*current*length*resistance/supply*100; Load voltage = supply-2*current*length*resistance
Worked example
Current (A): 10; One-way length (m): 20; Conductor resistance (ohm/m): 0.005; Supply voltage: 230.
Round-trip voltage drop: 2 V; Voltage drop: 0.87 %; Load voltage: 228 V.
Assumptions and limits
Use an appropriate resistance for conductor material, cross-section and temperature. Electrical design must follow applicable codes.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
Estimate DC voltage drop from current, one-way length and conductor resistance. The displayed figures use the inputs and formula shown on this page.
When this tool is useful
Use the voltage drop to compare a scenario, check an estimate, or verify a manual calculation.
Understanding your inputs
| Input | What to enter |
|---|---|
| Current (A) | Enter a number of at least 0.000001 and no more than 1000000000000. |
| One-way length (m) | Enter a number of at least 0.000001 and no more than 1000000000000. |
| Conductor resistance (ohm/m) | Enter a number of at least 0.000001 and no more than 1000000000000. |
| Supply voltage | Enter a number of at least 0.000001 and no more than 1000000000000. |
Frequently asked questions
What should I check before using the voltage drop result?
Use an appropriate resistance for conductor material, cross-section and temperature. Electrical design must follow applicable codes.
Is this voltage drop result exact?
It is exact for the stated mathematical model and entered values. Real-world results can differ when rates, timing, fees, definitions or measurement conditions differ.